Neuroprotective drugs that are highly effective in preventing neuronal cell death in vitro and preventing gray matter injury in vivo have not been successfully translated into therapies for human stroke. The reasons hypothesized to explain this failure of translation include the lack of effect of many neuroprotective treatments on white matter injury and a focus on hyperacute mechanisms that are not practical treatment targets in most patients with stroke. Ubiquitin C-terminal hydrolase L1 (UCHL1) is a multifunctional protein that is selectively expressed in neurons and axons throughout brain. UCHL1 plays an important role in axonal transport and maintaining axonal integrity as well as removing abnormal proteins via the ubiquitin proteasome pathway. UCHL1 regulates synaptic function and may be involved in memory function. Humans and mice with mutations in UCHL1 have extensive motor system abnormalities. We hypothesize that UCLH1 may play an important role in preserving axonal integrity and synaptic function promoting motor recovery after stroke. In the previous cycle of funding, we found that the 152 cysteine of UCHL1 binds reactive lipids and inactivates the enzyme. We constructed a mouse bearing a mutation that prevents binding at the site (C152A) and found that this mutation preserves axonal integrity and synaptic function and promotes motor recovery after cerebral ischemia in vitro and in vivo. We now have constructed a mouse bearing a mutation (C90A) that abolishes the UCHL1 hydrolase activity. In addition, we have constructed TAT-UCHL1 proteins that readily transduces neurons after systemic administration. We propose the following specific aims: Aim 1: Test whether the C90A mutation exacerbates gray and white matter integrity and exacerbates motor impairment after ischemia Aim 2: Test whether treatment with TAT-UCHL1 proteins will reduce gray and white matter injury and improve axonal conduction, synaptic function and motor behavior after ischemia. Aim 3 : Test whether the C152A mutation prevents white matter pathology and cognitive change in a model of vascular dementia in young and old mice. The broad long term objectives of these studies are to develop treatments that promote both gray and white matter preservation and functional recovery after stroke. These studies will improve scientific knowledge regarding the role of UCHL1 and in stroke and vascular dementia and test novel TAT-UCHL1 proteins in preclinical stroke models.